Mechanism of strontium sorption by the mixed nickel-potassium ferrocyanide based on hydrated titanium dioxide

The influence of surface modification of hydrated titanium dioxide (HTD) by mixed nickel-potassium ferrocyanide (NPF) phase on its selectivity for strontium and mechanism of strontium sorption was studied. It was shown that NPF-HTD sorbent possesses the same selectivity for strontium as the HTD sorbent, but higher static exchange capacity (SEC). The Henry distribution coefficient of strontium from a tap water with pH 7.8 +/- 0.1 was 10((3.0 +/- 0.3)) L kg(-1); the SEC, calculated according to Langmuir's isotherm, was 140 mg g(-1). Kinetic studies have shown that strontium sorption is limited by both internal and external diffusion as well as by the rate of chemical transformation of the NPF-HTD sorbent.